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Composition of tomatoes and tomato products in antioxidants (WG1) page 40
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vitamin C content (20 mg for mean fruit weight above 85g and 27 mg for mean fruit weight
25-85 g). Thus, cultural practices may have a great impact on tomato fruit vitamin C content.
Moreover, Grantz et al.(1995) demonstrated that total ascorbate contents were greatest in
leaves, with decreasing amounts in stems and roots and relatively constant levels in all stages
of fruit. Ascorbic acid content in developing fruit peaked at the light-red stage before full
colour was reached. Ascorbate Free Radical (AFR) reductase activity was inversely correlated
with enzyme activity in tissues examined. AFR reductase mRNA abundance increased
dramatically in response to wounding. AFR reductase may contribute to maintaining levels of
ascorbic acid for protection against wound-induced free radical-mediated damage. Indeed,
Moretti et al.(1998) have demonstrated that vitamin C content of fruit bruised at the breaker
stage was decreased of at least 15% in locular tissue and in pericarp tissue at the ripe stage in
comparison to unbruised fruit. Citing the U.S. Department of Agriculture (1997), Beecher
(1998) reported a Vitamin C content of cooked tomatoes of 230 mg/kg.
An investigation of literature knowledge of the influence of the main environment
factors and of the main cultural factors is presented below.
6.2.2. Influence of temperature
Little information was found about the influence of temperature on vitamin C content.
However, from various studies performed in control chambers by Hamner et al.(1945)
ascorbic acid content was only slightly, if at all, influenced by storage of the fruit for 10 to 14
days at temperatures from 19.5 to 32°C, at various relative air humidity. Relatively high
temperature of maturing or ripening fruit, whether on or off the plant, coupled with low light
intensity, may probably lead to reduction in ascorbic acid due to oxidation (Murneek et
al.1954). However, in greenhouse, Liptay et al.(1986) observed seasonal variations of cv.
Jumbo fruit vitamin C content from 70 to 230 mg/kg fresh matter at the mature-green stage, in
direct relation with temperature variations.
6.2.3. Influence of light
In experiences conducted by Hamner et al.(1945) on tomato cv. Bonny Best, a great
influence on fruit ascorbic acid content was produced by variations in light intensity previous
to harvest. Increases in the ripe fruit of 66% in ascorbic acid (from about 160-170 to 240-270